Human bodies as well as electronic devices are greatly influenced by electromagnetic interference (EMI) due to rapid increase in the use of electromagnetic waves.
A metal or a conductive material is used for shielding EMI in the prior art. The metal or the conductive material having a low impedance reflects and shields most of the electromagnetic waves due to a difference with impedance of air. However, shielding by reflection has a problem that secondary interference of reflected waves may occur.
Graphene is in the limelight as a substitute for conventional materials for shielding EMI. The graphene has advantages of low density and high corrosion resistance as compared with conventional material for shielding EMI such as metals, due to excellent electrical conductivity and large surface area. For these reasons, a nanocomposite material in which graphene, a conductive filler, and a polymer are complexed has been developed as a material for shielding electromagnetic wave. However, a content of the conductive filler should be increased to improve an electromagnetic wave shielding effect, which has problems of dispersion in the polymer, a decrease in impedance, an increase in weight, and an increase in cost.
Therefore, the present inventors found that at the time of manufacturing a multi-layer graphene-metal-polymer sheet for shielding electromagnetic wave having a multi-layer structure in which contents of conductive fillers are different from each other, instead of increasing a content of the conductive filler, the electromagnetic wave shielding effect was remarkably improved as compared with a sheet for shielding electromagnetic wave having a single-layer structure in which contents of conductive fillers are the same as each other, and completed the present invention.